Don't invalidate rect if it's covered by fully invalidated parent's visual rect

third_party/WebKit/LayoutTests/platform/mac/paint/invalidation/positioned-document-element-expected.txt

 {
   "layers": [
     {
       "name": "LayoutView #document",
       "bounds": [800, 600],
       "contentsOpaque": true,
       "drawsContent": true,
       "backgroundColor": "#008000",
       "paintInvalidations": [
         {
           "object": "LayoutView #document",
           "rect": [0, 0, 800, 600],
           "reason": "style change"
         },
         {
-          "object": "LayoutBlockFlow (positioned) HTML class='changed'",
-          "rect": [0, 0, 800, 50],
-          "reason": "style change"
-        },
-        {
           "object": "LayoutBlockFlow P",
           "rect": [8, 16, 784, 18],
           "reason": "forced by layout"
         },
         {
-          "object": "LayoutBlockFlow (positioned) HTML class='changed'",
-          "rect": [100, 100, 451, 50],
-          "reason": "style change"
-        },
-        {
           "object": "LayoutBlockFlow P",
           "rect": [108, 116, 435, 18],
           "reason": "forced by layout"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [108, 116, 435, 18],
-          "reason": "forced by layout"
-        },
-        {
-          "object": "LayoutText #text",
-          "rect": [8, 16, 435, 18],
-          "reason": "forced by layout"
         }
       ]
     }
   ],
   "objectPaintInvalidations": [
     {
       "object": "LayoutView #document",
       "reason": "style change"
     },
     {
@@ skipping 16 matching lines @@
       "object": "LayoutText #text",
       "reason": "forced by layout"
     },
     {
       "object": "InlineTextBox 'Tests that the entire viewport is painted with a floated html element.'",
       "reason": "forced by layout"
     }
   ]
 }